Conventionally, electric conductors are connected to contact or distribution elements, such as those used in primary or subsidiary distribution installations, by welding or screwing, or by winding the conductor around a terminal of square or rectangular section. All these methods strip the conductor before the connection is made, and this substantially increases the time taken by the operation. To obviate this disadvantage, use has been made more particularly in distribution installations of connecting means formed by so-called "insulation-displacing" or "self-stripping connection" terminals. Connecting devices of that kind comprise two lips each having a cutting edge which cuts the insulation when the conductor is introduced between the lips. The conductor is then gripped between the cutting lips, thus ensuring simultaneously its mechanical retention and the electric contact.
Such devices have other disadvantages, due to the fact that the cutting edges contact one another in the absence of the conductor, which must be forced in between the edges. Because of the pressure exerted by the two members of the fork, the conductor is subjected to an attack which may result in the appearance of a certain number of defects during operation. During introduction the conductor is subjected to rolling aggravated by planing, the main effect of this being to reduce the section of the conductor at the level of the connecting point. The pressure unequally distributed over the periphery of the conductor sets up stresses in the metal and may cause the start of breakage with an adverse effect on the satisfactory behavior of the connection, more particularly under vibrating conditions. If the conductor is a cabled conductor, there is a risk that some of the strands may be severed, thus reducing the section of the conductor and increasing the current density.